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WIN THIS RIFLE BUILD! BIG BORE .458 SOCOM AR15 GIVEAWAY!

Primary Arms Staff

9/9/2019 10:52 amwww.primaryarms.com

This Giveaway has ended. Congratulations to our winner, Tammy B. in Pennsylvania! You can view all current and past giveaways on our giveaway blog page.

It’s that time again. This time our giveaway rifle is a big bore thumper chambered in .458 SOCOM. As always, we’ve put together a list of the best parts and accessories to assemble one fantastic rifle with enough stopping power to take down any game animal or predator in North America with one shot. If you want to know how to build this rifle, read on. We lay out all the parts and why we selected them in the paragraphs below. First things first, though. A little background on this cartridge and why you would want to have a .458 SOCOM AR-15 for yourself.

.458 SOCOM is one of several rounds that came to light following Operation Gothic Serpent, which is more commonly known as the Battle of Mogadishu (or Black Hawk Down). The story starts at a beer and barbecue event, where SOCOM leaders were discussing the problems that 5.56 presented while fighting the Somalis. Some rangers were reporting that the .22-caliber cartridge wasn’t delivering enough force on target for reliable single-hit stops, so SOCOM started combing the market for a heavy-hitting alternative.

While there were many options, none completely satisfied the needs of a military cartridge, so Teppo Jutsu and Tromix partnered up to develop an alternative. Built for compatibility with the existing AR-15 platform, .458 SOCOM was the evolution of a cartridge once used by special forces in Vietnam: Barnes .458x1.5”. The SOCOM round was a heavy hitter, fitting only 10 in a standard 30-round mag, but delivering a real clap downrange. Bullet weights ranged everywhere from 250gr to a full 600gr, making it one of the most versatile cartridges ever developed for the AR-15.

While the exact details of .458 SOCOM’s use are classified, we know for sure that it was issued at some checkpoints, as the impact of the heavy round made it a natural engine-shredder. On the civilian market though, this cartridge has been beloved by hunters as a high-performance big game load that fits on your average AR15 lower. That said, our builds are anything but average. Here’s how we built a rifle to get the absolute best of the beloved .458 SOCOM cartridge…





Even though the .458 SOCOM cartridge is smaller than most big-bore rifle rounds, it still packs a heck of a punch. That extra oomph necessitates a robust upper receiver, such as the Aero Precision XL Upper Receiver. Made to the same world-class standard as all Aero Precision products, but with a larger ejection port to accommodate many big bore rounds, this upper was an easy pick for this build.




Since any lower receiver will do for a .458 SOCOM build, we chose one with a little flair. Spikes Tactical makes battle-ready products for the most demanding of circumstances, but they’re also known for their unique roll marks. This lower receiver features the Pipe Hitters Union Spade logo, adding some very critical style points. As you know, looking cool is half the battle.




Faxon Firearms is one of the industry’s best parts manufacturers, as their work can be found everywhere from the battlefield to the international space station. When it comes to barrels, few shops are as competent. Manufactured in Cincinnati, our .458 SOCOM Faxon barrel comes from 4150 chrome moly vanadium steel and features a gunner profile, QPQ Nitride finish, and a carbine length gas port for reliable cycling. Even with the added diameter, Faxon managed to cut the barrel’s weight to 1.75lbs, making it one of the lightest options on the market. To complete the setup, we added a Cross Machine Tool J.A.G. .875” gas block because it’s machined from solid steel and the set screw style ensures reliability won’t be an issue.




With all those weight savings, you may be wondering how the rifle will feel when recoiling. You’ll be surprised when you pull the trigger—but not in a bad way. We paired the Faxon barrel with a Faxon Gunner Muzzlok 3-port muzzle brake for the ultimate recoil mitigation. You’ll be shocked how comfortable this slugger can be.




When it comes to handguards, Aero Precision’s Enhanced M-LOK handguard is an easy pick. Its 15-inch length allows for a forward hold to mitigate muzzle rise when shooting this powerful rifle. This handguard accepts all M-LOK accessory attachments, has integrated Quick Detach sling points, and features a full picatinny top rail with alternating lightening cuts for your best compromise between weight and mounting capabilities.




FailZero bolt carrier group features a proprietary nickel boron (NiB) coating for enhanced material hardness and durability over the lifetime of the part. While other NiB BCGs exist, FailZero’s founders invented the proprietary NiB coating process, so you’re guaranteed the highest quality treatment. FailZero live-fire tests their products to ensure 100% customer satisfaction and reliability.




The buffer system is straight-forward. We went with the CMC complete buffer kit for this build because it’s got everything you need. This kit includes the castle nut and locking ring, and an endplate with a QD sling attachment. It’s a basic kit, but it’s well-made and reliable. Why complicate it further?




The stock for this build is the B5 Systems BRAVO, a SOPMOD-style stock with some ergonomic enhancements. It has an integrated QD mount, steel hardware, an ergonomic latch for quick length-of-pull adjustments, a rubber buttpad for increased comfort, and one of the most comfortable cheek weld sections of any polymer stock. It fits snug on the receiver extension for a rigid, rattle-free shooting experience.




A build of this caliber – no pun intended – necessitates a reliable, high-quality trigger. The most common complaints with MIL-SPEC triggers is that they can be gritty, aren’t crisp on the break, and are sometimes inconsistent. For many people, they’re still good enough to get the job done. But we are building this rifle to be a cut above average. For this build, we chose the ALG Defense Advanced Combat Trigger. It’s all the best things about MIL-SPEC triggers with none of the drawbacks. The extra processes of polishing all the engagement surfaces with an electroless nickel coating helps create a sharper, more consistent break. Its hammer, disconnector, and trigger pins have all been treated with Nickel Teflon to decrease friction and add durability. The trigger itself is treated with Nickel Boron for material hardness and longevity.




Primary Arms® Optics are known for incredible value, rugged dependability, and innovative designs. One innovation is the ACSS® Reticle, available in multiple configurations throughout our scope line. ACSS translates real world ballistics into the most advanced BDC reticle available. With wind holds, ranging ladders, and moving target dots, ACSS provides unparalleled speed on target.

The challenge with build, however, is that we need a system that can work with any caliber, not just the most commonly found AR-15 options. Enter the Primary Arms Silver Series™ 1-6x24mm SFP Scope with Illuminated KISS Reticle. Our KISS reticle is ideal for hunting and short-range calibers, where ranging is less important than having a quick, clear image of the target. The illuminated center chevron means you’ll have a fine aiming point to deliver exacting precision at zero. As a premium alternative, our Platinum Series™ 1-8x24 FFP Rifle Scope with Griffin MIL reticle has crystal clear glass, enhanced turrets, and a front focal plane design for accurate ranging at all magnifications. For the sake of this build, we stuck with the tried-and-true Silver Series optic.

For a mount, we used the Midwest Industries 30mm one-piece QD Scope Mount. The cantilever design provides room to get the exact eye relief you need, while the quick detach system makes installation or removal easy – no tools needed. At 8 ounces, it doesn’t add too much weight either. Finally, we rounded the upper off with a set of Midwest Industries Combat Rifle sights as a backup option.




To improve ergonomics and ease of handling this rifle, we’ve added a few finishing touches. The pistol grip we chose is from Hogue and features a rubber overmolded design with finger grooves. This ultra-comfortable grip fills the hand more completely with its contoured sides and provides complete control over your rifle, big bore or otherwise. The padded rubber is texturized to keep your hand from slipping around under sustained fire.

Rounding this build out is the Bravo Company Manufacturing GUNFIGHTER Ambidextrous charging handle with a large latch. Getting a firm, secure grip on this charging handle is easy as pie. Machined from 7075-T6 aluminum, this charging handle is built to endure abuse for years. The ambidextrous handles allow you charge the rifle with either hand, and the large latches extend out away from the scope for snag-free accessibility. The design of this handle eliminates one of the most crucial weak points on other ambidextrous charging handles, which is the pressure placed on the tiny roll pins holding the latches in place when the handle is being used. Instead, the force you apply when you pull on the latches is redirected into the main body of the solid aluminum handle. A raised lip on the top of the handle covers the space between the handle and the upper receiver, redirecting gas blowback away from the shooter’s face.

If you’re going to shoot this rifle, you want some magazines made to withstand the .458 SOCOM. We’ve thrown in a steel 10-round mag from E-Lander to make sure whoever wins this giveaway package has everything necessary to load up on ammo and hit the range.

Oh. Don't forget about ammo. Getting the right cartridge loading for .458 will depend on your application, but you can never go wrong with Black Butterfly Ammunition. When you talk about high-grade ammo, Black Butterfly stands out among the crowd, especially for .458 SOCOM. Their particular loading for the caliber is closest to the original spec, so you can run it with confidence in your new heavy hitter. Nick from Black Butterfly has graciously offered a couple boxes of their high-quality cartridges to our lucky winner, and we're happy to have their support. If you're into ammunition technology and development, definitely check out their Instagram page too.




Another build complete! We hope you took some inspiration from this big bore thumper and maybe even build one for yourself! There’s no denying the utility of being able to shoot such a large and powerful round from a compact and lightweight platform. Whether you’re out in a tree stand looking to put a trophy on the wall or doing some bear hunting, the .458 SOCOM round gets the job done. Even if you’re just punching paper, the power of .458 can bring a smile to any face!

If you want to take this rifle, we have good news: our giveaway is completely free. You can enter by visiting our Giveaway Landing Page, which has all the instructions to give you the best odds. Some terms and conditions apply. The giveaway ends August 18th, 2019, at 11:59pm CDT. At the end of the giveaway, the winner will be contacted via email on August 19th. Winner MUST be legally able to possess a firearm and pass a federal background check. Winner is responsible for all taxes. If the winner cannot meet the requirements necessary to take ownership of the firearm, the winner will be granted the total value of the prize package, $2,042.68, in cash. Exclusions apply, and no purchase is necessary. A full list of terms and conditions are visible through the Giveaway Landing Page.

If you’d like to build a clone of this rifle—or if you want to learn more about the components—all these parts are available at primaryarms.com.